According to a new report, men's sperm counts have decreased by a rate of 50% in the past 40 years in western countries.
The study, published in Human Reproduction Update on Tuesday, revealed that between 1973 and 2011, the concentration of sperm in the ejaculate of men in western countries has fallen 1.4% a year on average, leading to an overall drop of a little over 52%. Not only that, the decline doesn't seem to be leveling off, so the trend is likely to continue.
For the study, researchers at the Hebrew University and the Icahn School of Medicine at Mount Sinai drew data from 185 previous studies, finding significant decrease in sperm count among men from North America, Europe, Australia and New Zealand. As researchers noted, these men had not been selected based on their fertility status. Interestingly, no significant decline was found in South America, Asia and Africa, though far fewer studies were conducted in these regions.
"Given the importance of sperm counts for male fertility and human health, this study is an urgent wake-up call for researchers and health authorities around the world to investigate the causes of the sharp ongoing drop in sperm count, with the goal of prevention," Hagai Levine, MD, said in a press release.
Though the study doesn't delve into the possible reasons for the decline, Dr. Levine told Time that factors such as smoking, stress, and obesity could be to blame.
"One possible explanation is that men residing in Western countries over the last decades were exposed to new manmade chemicals during their life course, and there is more and more evidence that these chemicals hurt their reproductive function," he said. "We don't know for sure why this is happening, but our findings should drive massive scientific effort to identify the causes and modes of prevention."
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